The present invention relates to a method of enhancing a catalytic reaction and, more particularly, to a technique for a magnetic field catalyst process which utilizes magnetic field and charged particles to enhance catalytic reactions such as oxidation, reduction, denitrification, desulfurization and dechlorination by means of a semiconductor catalyst. This technology is useful for efficiently and economically processing chemical substances dissolved in gases or water in a large scale through such reactions as oxidation and. reduction, and is applicable specifically to chemical plants, remedial operation for environmental pollution, water purification, deodorization, air purification and agricultural/livestock farms.
A technology to activate or reform a fluid (gas or liquid) by applying a magnetic field to the gas or liquid has been known in the prior art. A technology is also widely known by which a semiconductor catalyst such as titanium oxide is irradiated with ultraviolet radiation thereby to cause oxidation, reduction, denitrification, desulfurization and dechlorination between the catalyst surface and gas or liquid which makes contact with the surface (photocatalyst process).
However, the effect and reaction of these techniques, when applied individually, have been insufficient and can last for only a short period of time.
In the case of the photocatalyst process, in particular, it is essential to apply a sufficient amount of ultraviolet radiation to the catalyst surface for the catalytic reaction to take place. Large scale commercialization of this technique has been hindered by such hurdles as various factors that hamper the efficient transmission of the ultraviolet radiation energy to the catalyst surface (stain on the catalyst surface, dispersion of light by fine particles, absorption and/or attenuation of the light energy by liquid phase, etc.) and low energy efficiency (catalytic effect per unit radiation energy).
The present invention aims at combining the prior art technologies of magnetic activation of a fluid and optical catalyst process to overcome the drawbacks of both technologies. Specifically, the present invention provides a method of enhancing the catalytic reaction of a semiconductor which is capable of making maximum use of the catalyst power of the semiconductor and sustaining, the power, by utilizing the electromagnetic induction energy imparted to charged particles which move in a magnetic field for the purpose of augmenting the catalytic reaction. Particularly it is intended to provide methods for reducing nitrogen oxides and dechlorinating organic chlorine compounds effectively by applying the technology of the present invention.
The present invention, which solves the problems described above, provides a method of enhancing the catalytic reaction, which comprises disposing a semiconductor catalyst in a fluid which includes charged particles, generating a magnetic field in the space wherein the semiconductor catalyst is disposed to impart electromagnetic induction energy to said charged particles, thereby enhancing the catalytic reaction of the semiconductor catalyst and a catalytic reaction apparatus comprising a semiconductor catalyst layer, a fluid supplying and discharging means which introduces a fluid including charged particles to the catalyst layer and discharges the fluid, and a magnetic field generator which generates a magnetic field in the fluid.
According to the present invention, charged, particles are preferably included in a fluid, which may be a gas or a liquid and makes contact with a semiconductor catalyst, and a magnetic field is generated in the space of the semiconductor catalyst where the fluid flows at a predetermined velocity, thereby imparting electromagnetic induction energy (Lorentz force) to the charged particles as shown in FIG. 4(a) and (b). The energy imparted to the charged particles is transferred to the catalyst when the particles make contact therewith, thereby enhancing the catalyst power and causing various reactions (oxidation, reduction, denitrification, desulfurization and dechlorination) to proceed efficiently.
The same effect can be achieved not only by moving the charged particles in the magnetic field but also by applying ultrasonic vibration to a fluid contained in a vessel such as reactor thereby oscillating the particles.
The semiconductor catalyst used in the present invention may be selected in accordance to the intended catalytic reaction from among oxides such as TiO2 (titanium dioxide), ZnO, Nb2O5, SrTiO3, PbNb2O6 and K4Nb6O17, sulfides such as CdS and ZnS, and organic polymer such as polyparaphenylene.
Among these, an dxide semiconductor is most preferably used and titanium oxide which undergoes oxidizing and reducing reactions is specifically preferable.
Charged particles carried by the, fluid may be the following substances. Nitrogen oxides, sulfur oxides, ozone and odor components, for example, may be used as the charged particles carried by the gas, For the charged particles carried by the liquid, nitrogen oxides; organic chlorine compounds such as trichloroethylene, tetrachloroethylene, trichloroethane, dioxins and trihalomethane; Na and Mg ions; and various artificial chemical substances may be used. Water molecules, which have polarity and can be regarded as charged in a broader sense of the word, may also be used as the charged particles according to the present invention. A molecule having localized electron distribution may be regarded the charged particle according to the present invention. These charged particles may not necessarily be subject to catalytic reaction.
The magnetic field used in the present invention may be either one-way magnetic field (DC magnetic field) or alternating magnetic field. Catalyst power of the oxide semiconductor is,enhanced by alternating the direction of the magnetic field at a high frequency. The magnetic field may be generated by either electromagnets or permanent magnets, which are arranged around or in a fluid path thereby to apply the magnetic field to the oxide semiconductor. The intensity of the magnetic field is preferably not less than 0.1 Tesla (1000 Gauss).
Methods for imparting kinetic energy to the charged particles are classified roughly into three types. The first is to cause the charged particles to undergo linear or circular movement unidirectionally (for example, by means of fluid pressure). The second is to excite the charged particles by ultrasonic or microwave energy so as to undergo random motion. The third is to move the charged particles through collision with the catalyst and viscosity of the catalyst surface by moving the semiconductor catalyst (for example, the semiconductor catalyst is caused to undergo rotation, reciprocal or random motion in the space occupied by the charged particles). The energy source for moving the charged particles may be (1) fluid pressure applied to the fluid, (2) various natural energy sources (potential energy, wind power, wave power, tidal wave energy, etc.), and (3) artificially generated energy (electric motor, internal combustion engine, ultrasound, microwave, etc.).
The semiconductor catalyst such as titanium dioxide ay be selected by giving consideration to the following factors.
(1) Catalyst Size
The catalyst is preferably made of small particles with a large surface area, although a bulk catalyst such as a sheet or a block may also be used.
(2) A Compound Selected to Best Suit the Intended Catalytic Reaction.
It is known that a compound of titanium dioxide and lead has a higher efficiency of generating methane from CO2 through photocatalytic reaction (carbon dioxide assimilation) about 30 times that of titanium dioxide only, and it is possible to decompose water into hydrogen and oxygen by ultraviolet radiation energy. (decomposition of water) by having ruthenium carried by barium tetratitanate. Based on various experiences and technologies acquired on the optical catalyst processes which employ oxide semiconductors or the like, a suitable compound can be selected for the intended catalytic reaction thereby to achieve the intended catalytic reaction more efficiently than in the prior art. This process may also be combined with the irradiation with light, as a matter of course.
(3) Combined Use of Other Catalysts
Catalyst power can be enhanced by combining activated carbon or iron oxide with the oxide semiconductors such as titanium dioxide.
(4) Combined Use of pH Control
Catalytic reaction of the present invention can be enhanced further by adding acid or alkali to the fluid so as to control the pH value to an optimum level.
(5) Catalytic Reaction Can be Enhanced By Adding H2O2, Ozone or Oxe2x88x923 to the Fluid, Thereby Increasing the Free Radicals Generated.
In order to put the present invention into practical operation, a catalytic reaction apparatus is used which comprises a semiconductor catalyst layer, a fluid supplying and discharging means that introduces a fluid including charged particles to the, catalyst layer and discharges the fluid, and a magnetic field generator which generates a magnetic field in the fluid. While the semiconductor catalyst layer may be disposed in a fluid passage or a tank such as a reaction vessel the catalyst layer may be of any proper type such as fixed bed or fluidized bed. There is also no limitation to the fluid supplying and discharging means which may be, for example, a pump. While there is no limitation to the magnetic field generator, one that is capable of applying an alternating-magnetic field is preferable as described above.
The present invention, which is capable of enhancing the catalyst power of the semiconductor and sustaining the power, can be applied to various fields as follows.
1. Organic chemical synthesis and decomposition plants in general.
2. Preventive and remedial measures against environmental pollution
(1) Denitrification, desulfurization and dechlorination of exhaust gas discharged from automobiles and waste incineration
(2) Denitrification, desulfurization and dechlorination of domestic waste water, industrial waste water, water discharged from industrial waste processing facility and water discharged from sewage treatment facility, removal and detoxification of various synthesized chemical substances.
(3) Remedial measures against eutrophication of lake, river, pond and seawater (denitrification, desulfurization, etc.)
(4) Efficient removal of various synthesized chemical substances from lake, river, pond and seawater and soil.
(5) A system to synthesize methane from carbon dioxide by means of natural energy, developed as countermeasure against global warming.
3. Health and sanitary applications
(1) Water purification (improving the water quality, removal and detoxification of various artificial substances) in public water works and privately owned purifying facilities (office building, hotel, hospital, home, etc.)
(2) Decomposition and/or removal of harmful substances (chlorine, trihalomethane, endocrine disrupters, etc.) included in potable water supply.
(3) water purification for swimming pool and public bath.
(4) Air purifier which combines deodorizing and sterilizing functions
4. Application to industrial process
(1) Supply of purified water or magnetically activated water for agriculture (stock breeding, poultry farming, horticulture, etc.)
(2) Water purification system for fish tank
(3) Supplying hydrogen fuel for fuel cell by means of a water decomposition system utilizing natural energy